The present invention relates to a method for inhibiting ammonia volatilization in poultry litter for improving bird weight gain and feed conversion. The present invention further relates to a method for reducing energy costs associated with poultry production and reducing heavy metals runoff from soil fertilized with a poultry manure-containing agricultural fertilizer.
One of the major problems encountered in raising chickens, turkeys or laying hens under confined conditions is ammonia volatilization, the production of excessive levels of ammonia gas (NH.sub.3). As volatilization occurs, ammonia levels can reach as high as 100-200 ppm in poultry houses. For over 30 years, researchers have shown that excessive ammonia build-up in poultry rearing facilities adversely affects both poultry and farm workers. Scarborough (Delaware Agric. Exp. Stn. Prog. Rep., NE8, 1957) and Valentine (Br. Poultry Sci. 5:149-159, 1964) both observed ammonia levels in the 60 to 70 ppm range in the atmosphere of poultry houses. Ammonia levels reaching as high as 100 ppm in commercial poultry houses have also been reported (Anderson et al., Poult. Sci. 43: 305-318 (1964)).
Anderson et al. demonstrated that when chickens, turkeys, guinea pigs, or mice were exposed continuously to 20 ppm ammonia, gross or histopathological signs of damage to the respiratory tract occurred after six weeks (Avian Dis. 8:369-379, 1964). They also found that chicks exposed to 20 ppm ammonia for 72 hours were much more susceptible to Newcastle Disease than controls reared in ammonia-free environments. Although all of the chickens had been exposed to the Newcastle Disease virus, only 40% of the chickens in the ammonia-free environment were infected, whereas 100% of the chicks were infected when exposed to ammonia. They indicated that these results may have been due to damage to the mucous lining of the respiratory tract.
High levels of ammonia have been shown to enhance the multiplication of Mycoplasma gallisepticum in the respiratory tract of chickens (Sato et al., Natl. Inst. Anim. Hlth. Qt., Tokyo, 13:45-53, 1973).
Charles et al. (British Poultry Science 7:177-187, 1966) found that keratoconjunctivitis developed in hens exposed to 100 ppm ammonia after six weeks, and egg production was depressed. Similarly, Strombaugh et al. found that high levels of ammonia adversely affected feed consumption and weight gain in pigs (J. Anim. Sci. 28:844, 1969).
In Europe, COSSH (Control of Substances Hazardous to Health) has set the limit of human exposure to ammonia at 25 ppm for an eight hour day and 35 ppm for a 10 minute exposure (Williams, Proc. Ark. Nutrition Conference, Fayetteville, Ark., pp. 14-29, 1992). With current production practices, these levels are often exceeded in broiler houses.
The number one complaint received by state and federal environmental agencies each year against animal producers involves odor. Since ammonia comprises a large portion of the odor associated with poultry litter, measures to control odor must incorporate strategies that reduce ammonia volatilization.
There are several litter amendments currently on the market which supposedly reduce ammonia volatilization. Among these are MLT (Multi-Purpose Litter Treatment), PLT (Poultry Litter Treatment), De-odorase, and Ammonia Hold. However, there are no published reports based on valid scientific studies in which these products were tested. Most of the products depend on testimonials from individuals for their sales. A need, therefore, exists for reproducible studies comparing these products with other compounds, which based on their chemical or physical properties, would likely reduce volatilization.
In addition to the ammonia volatilization, another major problem commonly associated with poultry litter is the amount of phosphorus (P) runoff which enters the aquatic system from fields receiving poultry litter. Phosphorus runoff is the primary cause for eutrophication in lakes and other freshwater bodies. Tighter controls of point sources of phosphorus, such as municipal waste water treatment plants, have resulted in decreased phosphorus loading from point sources into the aquatic environment in the last few decades. However, improvement of water quality has not always been observed when point source phosphorus loads were reduced. Therefore, attention is currently being focused on non-point sources of phosphorus such as agricultural runoff. One of the major sources of phosphorus runoff from agricultural lands is animal waste.
Several investigators have characterized phosphorus runoff from fields receiving poultry manure (Edwards et al., J. Environ. Qual. 22:361-365, 1993; McLeod et al., J. Environ. Qual. 13:122-126, 1984; Westerman et al., In (R. J. Smith, ed.) Livestock waste: A renewable resource. Proc. Fourth Int. Symp. on Livestock Wastes, 289-292. St. Joseph, MI:ASAE, 1980; and Westerman et al., Transactions of the ASAE 26:1070-1078, 1983). These studies have all shown that phosphorus runoff increases as the manure or litter application rate increases and as rainfall intensity increases. Drying time has also been shown to be an important parameter with respect to phosphorus runoff. With longer periods between application and rainfall, phosphorus runoff was greatly reduced (Westerman et al., supra, 1980; Westerman et al., supra, 1983). Recent studies have shown high concentrations of phosphorus (14-76 mg PL.sup.-1) in runoff from pastures receiving poultry litter, most of which is dissolved inorganic phosphorus (.apprxeq.85%), with only small amounts of particulate phosphorus (Edwards et al., supra). Sonzogni et al. found that dissolved inorganic phosphorus is directly available to algae and concluded that best management practices used to decrease phosphorus runoff should consider the bioavailable-phosphorus load, rather than focusing on the total-phosphorus load (J. Envir. Qual. 11:555-563, 1982).
Rapid and concentrated growth of the poultry industry, fueled by the demand for low-fat meat, has raised concerns in several states regarding water quality. Arkansas, for example, is the number one poultry producing state in the U.S., with approximately one billion broilers produced per year. Each broiler produces approximately 1.5 kg of poultry litter over a 10-week growing cycle (Perkins et al., Bull. NS 123, Georgia Agri. Exp. Station, Athens, Ga., 1964). This litter contains 8-25.8 g P kg.sup.-1, with soluble reactive phosphorus levels up to 4.9 g P kg.sup.-1 (Edwards et al., Bioresource Tech. 41:9-33, 1992). Runoff of phosphorus from fields receiving poultry litter has been speculated to be one of the primary factors affecting water quality in Northwest Arkansas. High bacterial counts and high biochemical oxygen demands have also been attributed to litter.
Currently, there is a movement to limit the amount of chickens produced in a given area to minimize phosphorus loading into the aquatic system. In the next 5 years, the U.S. Environmental Protection Agency will require all farms that produce in excess of 15,000 birds per year to construct detention ponds capable of holding all the runoff from a 25 year storm. As an alternative, poultry producers could be forced to transport litter to areas with low soil phosphorus and/or build litter storage facilities at a significant cost to poultry producers, and ultimately the consumer. An alternative solution is clearly needed to reduce soluble phosphorus levels in poultry litter.